The EL elements are elements, in which holes and electrons injected from two electrodes facing each other bind in a light-emitting layer to each other and a fluorescent material presented in the light-emitting layer is excited by the energy, emitting a light in the color inherent to the fluorescent material, and are attracting attention as a self-luminous flat display element. In particular, organic EL displays employing an organic material as the light-emitting material are higher in emission efficiency, for example allowing high-brightness emission even at an applied voltage of less than 10 V, and allow light emission in a simple element structure. Thus, their application to low-priced simplified display used for advertisement and others, which displays a particular pattern by emission, is highly expected.
Generally, in production of a display employing an EL element, an organic EL layer comprising layers such as a light-emitting layer, a hole-injecting layer, a hole-transporting layer, an electron-injecting layer, and an electron-transporting layer is patterned. Various patterning methods such as a vapor deposition of the light-emitting material through a shadow mask, a printing by inkjet, a decomposition of a particular light-emitting colorant by UV irradiation, a screen printing has been proposed as the methods of patterning the light-emitting layer. In the case of the inkjet printing method, formation of a patterned barrier (bank) and ink-repellent treatment of the barrier were proposed for obtaining a high-definition ultrafine pattern (e.g., see Patent Documents 1 and 2). In addition, a method using a photocatalyst enabling high-definition patterning has also been proposed as the methods of patterning the light-emitting layer (see e.g., Patent Documents 3 and 4).
The method using a photocatalyst and patterning the organic EL layer utilizes the change in wettability of the photocatalyst-containing layer caused by the energy irradiated to the photocatalyst-containing layer and the subsequent action of the excited photocatalyst. In other words, an organic EL layer is patterned, while the difference in wettability is utilized in patterning. Thus, since the method of using a photocatalyst and patterning the organic EL layer allows patterning by using the difference in wettability generated only by energy irradiation, it is a method useful for drastic reduction in the labor demanded for patterning the organic EL layer.
However in such a method of using a photocatalyst and patterning the organic EL layer, the photocatalyst such as titanium oxide is normally granular and thus, the surface of the photocatalyst-containing layer is often roughened. This unfavorably leads to increase in the barrier at the interface between the organic EL layer such as light-emitting layer and the photocatalyst-containing layer, hinders transport of electric charges, and deterioration in emission characteristics. The surface roughening of the photocatalyst-containing layer also causes problems such as unevenness in thickness of a relatively thin light-emitting layer and short circuiting between electrodes.
Proposed to overcome the problems above were methods of patterning the EL layer by using the difference in wettability, specifically by using a substrate having a photocatalyst-containing layer, providing a layer that changes its wettability under the action of a photocatalyst caused by energy irradiation and a photocatalyst-containing layer at positions facing each other, and irradiating the layers with energy to change the wettability of the layer surface (see e.g. Patent Documents 5 and 6).
Patent Document 5 discloses a method of patterning an organic EL layer by using a charge injecting/transporting layer that changes its wettability under the action of a photocatalyst caused by energy irradiation. The charge injecting/transporting layer contains: a binder such as organopolysiloxane and a photocatalyst, or materials commonly used in charge injecting/transporting layer such as polyethylenedioxythiophene/polystyrenesulfonic acid (PEDOT/PSS). In the former case, the surface roughening of the charge injecting/transporting layer is desired to be reduced further, because it contains a photocatalyst. In the latter case, the charge injecting/transporting layer may not show favorable change in wettability, because it contains the materials commonly used in the charge injecting/transporting layer.
Patent Document 6 discloses a method of patterning an organic EL layer, by using a wettability variable layer that changes its wettability under the action of a photocatalyst caused by energy irradiation. The wettability variable layer preferably contains a conductive material in order to enable transportation, for example, of holes. However, although Patent Document 6 describes the method of producing the pattern forming body in detail, it does not describe the configuration of the organic EL element and the preparative method thereof in detail.
Alternatively, Patent Document 5 discloses a method of patterning an organic EL layer by using a decomposing-removing layer that is decomposed and removed under the action of a photocatalyst caused by energy irradiation. It is a method of patterning an organic EL layer by using the difference in wettability between: the region of the decomposing-removing layer where the undercoat layer thereof is exposed by decomposition and removal of the decomposing-removing layer under the action of a photocatalyst caused by energy irradiation, and the region retaining the decomposing-removing layer because no energy is irradiated thereto. In this case, the organic EL layer is formed on the region where the undercoat layer below the decomposing-removing layer, for example electrode layer, is exposed.    Patent Document 1: Japanese Patent No. 3601716    Patent Document 2: Japanese Patent No. 3646510    Patent Document 3: Japanese Patent Application Laid-Open (JP-A) No. 2001-257073    Patent Document 4: JP-A No. 2002-231446    Patent Document 5: JP-A No. 2004-71286    Patent Document 6: JP-A No. 2005-300926